Incidence of dementia among participants and nonparticipants in a longitudinal study of cognitive aging

David S. Knopman, Rosebud O. Roberts, V. Shane Pankratz, Ruth H. Cha, Walter A. Rocca, Michelle M. Mielke, Bradley F. Boeve, Eric G. Tangalos, Robert J. Ivnik, Yonas E. Geda, Ronald C. Petersen

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Although rates of incident dementia have been reported from several populations, the impact of nonparticipation on dementia incidence in studies of cognitive aging is unknown. In 2004, investigators with the Mayo Clinic Study of Aging selected persons aged 70-89 years from an enumeration of all Olmsted County, Minnesota, residents (ageand sex-stratified random sample). Of 4,398 potential participants, 2,050 agreed to undergo an in-person health assessment. Those participants were reevaluated in person using standard diagnostic procedures approximately every 15 months over a median follow-up period of 5.7 years (through September 15, 2013). There were 1,679 persons who refused any participation. A trained nurse abstractor reviewed the medical records of nonparticipants using the Rochester Epidemiology Project's medical record linkage system a median of 3.9 years after refusal. Nonparticipants had a higher prevalence of dementia than participants evaluated in person (6.5% vs. 3.3%;P<0.0001). The standardized incidence of dementia was not significantly higher among the nonparticipants (23.2 per 1,000 person-years) than in those evaluated in person (19.6 per 1,000 person-years; hazard ratio = 1.17, 95% confidence interval: 0.95, 1.43 (P =0.13); adjusted for education and sex, with age as the time scale). The small, nonsignificant impact of nonparticipation on rates of incident dementia is reassuring for future studies based on incident dementia cases.

Original languageEnglish (US)
Pages (from-to)414-423
Number of pages10
JournalAmerican journal of epidemiology
Issue number4
StatePublished - Aug 15 2014
Externally publishedYes


  • Aging
  • Cognition
  • Cognitive aging
  • Dementia
  • Epidemiologic methods
  • Incidence
  • Prevalence

ASJC Scopus subject areas

  • Epidemiology


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